[lld] [lld] enable installing lld headers as part of distribution (PR #127123)

[Maksim Levental via llvm-commits]

makslevental wrote:

> I am sure.

I'm not saying I disagree with the clang behavior, I'm saying that the behavior I'm seeing is exactly what you expect i.e. `-DLLVM_DISTRIBUTION_COMPONENTS=lld` only installs `lld` itself and not the headers.

> State the behavior of lld;lld-headers;lld-libraries respectively when they are used in LLVM_DISTRIBUTION_COMPONENTS.

It is exactly what you expect and what this PR implements:

### `DLLVM_DISTRIBUTION_COMPONENTS=lld-headers`

```bash
(base) mlevental at maksims-MacBook-Pro llvm-project % rm -rf llvm-install-release                                                                                                                                                                             
(base) mlevental at maksims-MacBook-Pro llvm-project % cmake -GNinja -B build -S llvm -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS=lld -DLLVM_TARGETS_TO_BUILD=host -DLLVM_DISTRIBUTION_COMPONENTS=lld-headers -DCMAKE_INSTALL_PREFIX=llvm-install-release
...
(base) mlevental at maksims-MacBook-Pro llvm-project % cmake --build build --target install-distribution
[0/1] cd /Users/mlevental/dev_projects/llvm-project/build/tools/lld && /opt/homebrew/Cellar/cmake/3.29.3/bin/cmake -DCMAKE_INSTALL_COMPONENT="lld-headers" -P /Users/mlevental/dev_projects/llvm-project/build/cmake_install.cmake
-- Install configuration: "Release"
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/ErrorHandler.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Filesystem.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/TargetOptionsCommandFlags.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Version.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/DWARF.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Driver.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/LLVM.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/CommonLinkerContext.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Strings.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Timer.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Args.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Arrays.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Memory.h
-- Installing: /Users/mlevental/dev_projects/llvm-project/llvm-install-release/include/lld/Common/Reproduce.h
```

### `DLLVM_DISTRIBUTION_COMPONENTS=lld-libraries`

```bash
(base) mlevental at maksims-MacBook-Pro llvm-project % rm -rf llvm-install-release                                                                                                                                                                             
(base) mlevental at maksims-MacBook-Pro llvm-project % cmake -GNinja -B build -S llvm -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS=lld -DLLVM_TARGETS_TO_BUILD=host -DLLVM_DISTRIBUTION_COMPONENTS=llvm-libraries;lld-headers -DCMAKE_INSTALL_PREFIX=llvm-install-release
...
(base) mlevental at maksims-MacBook-Pro llvm-project % cmake --build build --target install-distribution
...
(base) mlevental at maksims-MacBook-Pro llvm-project % ls llvm-install-release                     
include	lib
(base) mlevental at maksims-MacBook-Pro llvm-project % ls llvm-install-release/include             
llvm-c
(base) mlevental at maksims-MacBook-Pro llvm-project % ls llvm-install-release/lib | grep "liblld*"
liblldCOFF.a
liblldCommon.a
liblldELF.a
liblldMachO.a
liblldMinGW.a
liblldWasm.a
```

Can you please try a fresh/clean build on this commit to confirm. If you're not able to I can setup a test/demo/repro repo.



https://github.com/llvm/llvm-project/pull/127123